1. Field of the Invention
The present invention relates to a frequency selective digital transmission apparatus and, more particularly, to a technique of selecting one of a high performance mode, a general mode, and a low power mode according to a symbol rate and a clock in use varying according to various applications, and selectively using one of a high speed spreading scheme employing a frequency selective spreader having a multi-structure providing a high data transmission efficiency and a low speed spreading scheme having a transmission performance superior to a transmission efficiency in each mode, in a frequency selective digital transmission apparatus, which uses a frequency selective spreading code in order to avoid a frequency band to which noise power around a human body is concentrated, compared with other bands, and uses a limited frequency band up to a frequency band at which the strength of a signal transmitted by using the human body as a waveguide is stronger than the strength of a signal radiating to the exterior of the human body.
2. Description of the Related Art
Korean Patent No. 829865, filed in 2006 by the same inventor of the present invention and registered in 2008 and entitled “A human body communication system using a limited pass band and method thereof,” discloses a human body communication system implemented by using a pass band limited from 5 MHz band to 40 MHz and performing scrambling, channel coding, interleaving, spreading, and the like, by using a unique user identification information (ID).
Also, Korean Patent Application No. 2007-0087869 filed in 2007 and entitled “Modulation and demodulation method using a frequency selective baseband and apparatus thereof” discloses a frequency selective multi-structure capable of increasing a transmission data rate as well as improving a processing gain of an overall system by using serial-to-parallel conversion, frequency selective baseband transmission, and a limited number of spreading codes.
However, a technique of optimizing a frequency selective digital transmission apparatus in consideration of a clock speed, a frequency band in use, a maximum data rate, power consumption, and the like, appropriate for each application in a human body communication system performing various applications has never before been presented.